Cold oxygen plasma induces changes on the surface of carbon materials enhancing methanogenesis and N2O reduction in anaerobic sludge incubations

BACKGROUND Conductive materials, such as activated carbon (AC), graphene and biochar, have recently been applied for enhancing methane (CH4) production in anaerobic digesters. However, few efforts have been made to develop engineered conductive materials for these purposes. The aim of this work was to synthesize carbon materials from pecan nut shells and peach stones to apply them in anaerobic sludge incubations for enhancing the methanogenic activity, as well as the reduction of nitrous oxide (N2O). RESULT Addition of conductive materials increased up to six-fold the maximum CH4 production rate. Moreover, oxidation of these carbon materials with cold oxygen plasma enriched their surface with redox functional groups (e.g. quinones), so that their application further increased the methanogenic production rate up to 11-fold as compared to controls lacking conductive materials. Furthermore, the reduction rate of N2O was increased several orders of magnitude in the presence of synthesized carbon materials, which constitutes the first demonstration that conductive materials can significantly increase the reduction rate of this greenhouse gas. CONCLUSION Results indicate that there is great potential to develop engineered conductive materials to enhance both the production of CH4 and the reduction of N2O from wastewater treatment plants (WWTP), which may contribute to achieve more efficient processes. (c) 2019 Society of Chemical Industry